Devices for sorting plane rectangular postal objects (letters, postcards, documents in envelopes, magazines, etc.) are known, which comprise:                a module for acquisition and singulation of postal objects, which receives at input packs (also referred to as files) of postal objects and is designed to generate at output singulated postal objects, i.e., ones physically separated from each other; and        a sorting device, coupled at input with an outlet of the acquisition and singulation module and designed to address, by means of appropriate exchanges, each singulated postal object received at input towards a respective outlet belonging to a series of accumulation outlets with which the sorting module is provided.        
The sorting device is designed to perform operations of sending of the postal objects to the outlets, said operations being designed to enable, following upon execution of an initial step and a final step, formation in the outlets of groups of postal objects that are sequenced, i.e., ordered according to successive delivery points.
As is known, the sequenced postal objects can be conveniently delivered in succession by a postman, who proceeds along a postal path in which the delivery points are physically located.
It may be shown that for a sorting device provided with n physical separations (stacker, bin, container outlets etc.) n*n delivery points can be sequenced in two passes or steps (for example, said initial step and final step).
Known solutions envisage the interposition of an intermediate sequencing step between the initial one and the final one. In known solutions, this requires that at least all the mail regarding the additional addresses, which may be the majority, must be:                fed onto the sorting system, hence requiring additional processing time; and        buffered within the sorting system, which comprises, in this case, accessory pigeon-holes for ordered housing of the sorted mail, up to the end of the intermediate sorting step, this requiring a considerable storing capacity.        